Fiber optic transmission systems and methods are widely recognized as the most efficient way to transmit large amounts of data over long distances. An important metric for these systems and methods is called spectral efficiency. Spectral efficiency is a measure of the rate at which data can be transmitted in a given amount of optical spectrum, usually expressed in bits/s/Hz. The size of the available optical spectrum is determined by factors such as the wavelength of low attenuation in transmission fiber, bandwidth of optical amplifiers, and availability of suitable semiconductor lasers and detectors. For example, the C-band may generally include optical spectrum of 1530-1565 nm which corresponds to the amplification range and bandwidth of erbium-doped fiber amplifiers (EDFAs). Given that there is a finite useable spectral range, the spectral occupancy and a given bit-rate of channel, the spectral efficiency of a dense wave division multiplexing (DWDM) system then determines the maximum information carrying capacity. As data demands increase, there is consistently a need for more information carrying capacity given the finite constraints on the useable spectral range.